This is a multi-center, hospital based, cross-sectional study based on data from patient medical records, including laboratory results. The study will include adult patients with chronic (> 1 year duration) primary Immune Thrombocytopenia (ITP) only. Patients will be identified based on a laboratory confirmed diagnosis of ITP in the medical records, where there is also a physician-confirmed diagnosis of primary ITP. If patients consent to take part in the study, a routine clinical visit will also serve as the study visit. Patients who do not have a routine visit scheduled during the study period but who would otherwise be eligible may be contacted by the site. In such cases, clinicians may use their discretion to schedule a visit specifically for study purposes.

All study participants will have a routine blood test as part of their standard clinical care at the study visit, and this same procedure will be used to collect supplementary blood samples to assess a variety of biomarkers.

Data will be collected using a combination of chart review, clinical outcome assessment administration, and laboratory results through blood tests.

Inclusion Criteria:

• Patient diagnosed with chronic (ITP with > 1 year duration) primary ITP living in the USA or the UK:

  • On ITP pharmacologic treatment, , including on-demand treatment strategy, regardless of last platelet count (below or above 100 x 10^9 counts/L);
  • Patients with their most recent platelet count >50 x 109 counts/L) and without any ITP-specific treatment for 1 year or less.

• Adult patient who are 18 years or older at index date

• Patient who has received at least one initial first line ITP therapy (CS/ IVIg/ANTI d) with initial response as of index date and indicated by one of the following:

  • Platelet count ≥ 50 x 10^9 counts /L; OR
  • Platelet count ≥ 30 x 10^9 counts /L with at least a two-fold increase from baseline within 1 month since start of treatment, as per ASH 2019 guidelines; OR
  • A medical record of initial response as determined by clinical judgement, considering documented platelet count along with overall patient condition and relevant medical factors.

• Patients whose medical history related to the study objectives are available from the site covering 12 months prior to index date.

• Patient provided informed consent to participate in the study.

Exclusion Criteria:

• Secondary ITP.
• Patients with their most recent platelet count >50 x 10^9 counts/L and without any ITP-specific treatment for more than 1 year.
• Patients with recent or active infection recorded 14 days or less before index date; patients with uncontrolled chronic infections or who were recently diagnosed with a chronic infection (≤14 days of index date).
• Patients with vaccination in 28 days before index date.
• Patients treated with rilzabrutinib on or before index date.
• Patients who participated in an interventional clinical trial for any investigational drug in the 180 days prior to index date.

The source population for this study will be patients treated for primary chronic Immune Thrombocytopenia at one of the four study centers in two countries (3 centers in the USA, 1 center in the UK).

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org